1. Field of the Invention
Embodiments of the subject matter disclosed herein generally relate to magnetic components, and more particularly, to a multiple mega-Watts (MW) level dry type power transformer operating at voltage levels in the kV range and capable of operating at a fundamental frequency ranging from about hundreds of Hz up to about 1 kHz in a power converter.
2. Description of the Prior Art
Most commercial solutions presently implement dry-type transformers which are either air-cooled or which implement direct cooling for windings (such as hollow metallic tubes that conduct both a cooling fluid and electrical current in the tube). Air-cooled transformers at this power level and frequency approach sizes that are undesirably large. Direct-liquid-cooled tubes exhibit poor packing factors and result in large windows for the winding(s). Further, directly cooled windings exhibit high losses since they cannot be transposed and stranded like litz-wire.
The liquid cooling system of the transformer preferably shares the cooling liquid with the cooling circuit of a power converter. The cooling fluid(s) in modern power electronics is typically in direct contact with several parts of the system. It is known that de-ionized (DI) water interacts with aluminum heat sinks of the converter that are used for cooling semiconductors. The use of copper for cooling tubes of the transformer in such a system should desirably be avoided in the thermal path to eliminate electrochemical interaction that leads to corrosion of the aluminum heat sinks, thus ruling out any direct cooling solution via hollow copper tubes for the transformer. Directly cooled transformer solutions using indirect cooling allows use of Litz wire resulting in a much lower coil loss.
In view of the foregoing, there is a need for a multiple MWs level dry type power transformer capable of operating at a fundamental frequency ranging from about hundreds of Hz up to about 1 kHz in a power converter. The power transformer should avoid the foregoing electrochemical effects, provide a superior packing factor when compared to a hollow aluminum design, and should have a substantially higher efficiency than known solutions.